function ds = ZermeloAdjAndSys(t, s)
x = s(1:2);
lambda = s(3:4);
u = ???; % Choose u such as Hu = 2*u + la2 = 0
ds = zeros(4,1);
ds(1) = ???;
ds(2) = ???;
ds(3) = ???;
ds(4) = ???;